street trees, over 500 street trees on the city's right-of-way, and 362 structures. that includes many of our stairways, our bridges, tunnels, and other structures. the department's essential services, we respond to over 100,000 311 calls every year for street cleaning, illegal dumping, graffiti abatement, potholes, tree maintenance. we mechanically sweep over 146,000 miles of street, remove over 30,000 tons of debris on the streets of san francisco, and fill over 12,000 potholes. we inspect over 2.7 million square feet of sidewalk and we engage and manage thousands of volunteers to help us keep the city clean.